The invention relates to an infinitely variable traction roller transmission in which power is transmitted through traction rollers pivotally supported between toric input and output disks.
To enable such toroidal traction roller motion transmissions to efficiently transmit large torques at high speeds over a long period of time, the traction rollers may be positioned inwardly of the center of the toroidal cavity between the toric disks to reduce spin. The traction rollers are engaged with the toric disks with considerable forces causing large surface contact loads.
During rolling of the traction rollers on the toric disks, although reduced, there is still some finite spin at the engagement points which results in detrimental fluid shear losses in the traction roller contact areas. It is therefore desirable to provide arrangements with "zero spin". "Zero spin" as concerns this discussion, is a state wherein of two bodies which are in rolling contact, the contact tangent normal to the direction of rolling, and the axes of rotation of the two bodies all intersect in a single point. For a toric transmission to have zero spin, this state must be true for both contacts, that is, for the contacts of the traction roller with the input and output toric disks, and at all times, that is, all the different traction roller pivot positions. In practice, because of manufacturing tolerances and deflections and other influences, this theoretical condition may not be met at all times.
It is the object of the present invention to provide a traction roller transmission with a traction roller support arrangement and with toric disk surfaces which together provide for essentially zero spin motion transmission.